EP4620594A1

EP4620594A1 - Mold apparatus for molding press, and press molding method

Info

Publication number: EP4620594A1
Application number: EP23906852.1A
Authority: EP
Inventors: Hideki Shudai; Daisuke Miyazaki; Keisuke Yamada; Nobumitsu IDA; Katsuya KITAGAWA; Akihiro HANABATA
Original assignee: Mayekawa Manufacturing Co
Current assignee: Mayekawa Manufacturing Co
Priority date: 2022-12-21
Filing date: 2023-12-13
Publication date: 2025-09-24
Also published as: KR20250110292A; JP2024089230A; EP4620594A4; WO2024135487A1; CN120322299A

Abstract

A forming press die apparatus according to an embodiment is a forming press die apparatus used in a forming press machine, including: a pair of upper and lower dies; and a heater for heating the dies.

Description

TECHNICAL FIELD

The present disclosure relates to a forming press die apparatus and a press-forming method.

BACKGROUND

For example, a press-forming method is known for processing a workpiece, such as a thin metal sheet, into a desired shape by press forming.
For example, Patent Document 1 describes forming an uneven heat transfer surface of a heat exchange plate for a plate-type heat exchanger by pressing a thin metal sheet with a pressing apparatus.

Citation List

Patent Literature

Patent Document 1: JP2007-285682A

SUMMARY

Problems to be Solved

For example, in press forming to form irregularities in a thin plate such as the heat exchange plate as described in Patent Document 1, if relatively high forming accuracy is required for the workpiece after forming, the effect of variations in the tensile strength of the workpiece may not be ignored.
The tensile strength of the workpiece depends on the temperature of the workpiece as well as the variation allowed by the material specifications of the workpiece. Therefore, for example, when the tensile strength of the workpiece is near the upper limit of the range allowed by the material specifications of the workpiece, the tensile strength of the workpiece may further increase in environments with low ambient temperature, such as in winter, and there is a risk that a specified pressing pressure may be insufficient to achieve the required forming accuracy of the workpiece after forming.
In such cases, it is conceivable to take measures such as extending the holding time during which the workpiece is held under pressure or increasing the pressing pressure, for example. However, extended holding time leads to a decrease in productivity due to the longer time required for the pressing process. Alternatively, increasing the pressing pressure is a measure, provided that the increased pressing pressure remains within the pressure capacity of the forming press machine.
However, if there is little margin in the pressure capacity of the forming press machine, it may be difficult to address the issue by increasing the pressing pressure.
In view of the above, an object of at least one embodiment of the present disclosure is to stabilize the forming accuracy of a workpiece that has been press formed by a forming press machine.

Solution to the Problems

(1) A forming press die apparatus according to at least one embodiment of the present disclosure is a forming press die apparatus used in a forming press machine, including: a pair of upper and lower dies; and a heater for heating the dies.
(2) A press-forming method according to at least one embodiment of the present disclosure is to press form a workpiece by a forming press machine using the forming press die apparatus described in the above (1).

Advantageous Effects

According to at least one embodiment of the present invention, it is possible to stabilize the forming accuracy of a workpiece that has been press formed by a forming press machine.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the overall configuration of a forming press die apparatus according to an embodiment.
FIG. 2 is a schematic front view of the forming press die apparatus according to an embodiment.
FIG. 3 is a flowchart showing the processing procedure in a press-forming method using the die apparatus according to an embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions, and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present disclosure.
For instance, an expression of relative or absolute arrangement such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial" shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.
For instance, an expression of an equal state such as "same" "equal" and "uniform" shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.
Further, for instance, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved.
On the other hand, an expression such as "comprise", "include", "have", "contain" and "constitute" are not intended to be exclusive of other components.
FIG. 1 is a diagram showing the overall configuration of a forming press die apparatus according to an embodiment.
FIG. 2 is a schematic front view of the forming press die apparatus according to an embodiment.
A forming press die apparatus 1 according to an embodiment is a forming press die apparatus used in a forming press machine 3. In the following description, the forming press die apparatus 1 is also simply referred to as die apparatus 1. The die apparatus 1 according to an embodiment includes an upper die unit 1U and a lower die unit 1L. In FIGs. 1 and 2, guides or other components for guiding the upper die unit 1U to move in the up-down direction relative to the lower die unit 1L are omitted. Also, in FIG. 2, the upper die unit 1U and the lower die unit 1L are shown with more space therebetween than after assembly of the die apparatus 1.
Further, the die apparatus 1 according to an embodiment is equipped with a heater control device 9 for controlling a heater 21, which will be described below.
The die apparatus 1 according to an embodiment is installed on a bolster 3a of the forming press machine 3. By pressing down the upper die unit 1U by a slide 3b that is movable in the up-down direction, a thin metal sheet, a workpiece 11, is pressed into a desired shape by a pair of upper and lower dies 8, which will be described below.

(Upper die unit 1U)

In the die apparatus 1 according to an embodiment, the upper die unit 1U includes an upper holder 5U, an upper liner 6U, and an upper die 8U as main components.
The upper holder 5U is a holder for holding the upper die 8U of the pair of upper and lower dies 8, and the upper liner 6U.
The upper liner 6U is a liner that is disposed between the upper holder 5U and the upper die 8U and is held by the upper holder 5U together with the upper die 8U. The upper liner 6U has a heater 21 attached, as described below, and is a separate member from the pair of upper and lower dies 8.
In the die apparatus 1 according to an embodiment, the upper liner 6U is attached to the lower surface of the upper holder 5U.
In the die apparatus 1 according to an embodiment, the lower surface of the upper liner 6U has a plurality of grooves 6a. The plurality of grooves 6a are grooves for placement of heaters 21 in the upper liner 6U to heat the upper die 8U. In the example shown in FIG. 2, the plurality of grooves 6a extend in the depth direction and are arranged at intervals in the right-left direction in the figure.
As described above, the heater 21 is disposed in each of the plurality of grooves 6a. The heater 21 is, for example, a rod-shaped heater, such as a sheathed heater.
In the die apparatus 1 according to an embodiment, a plurality of holes 6b are formed from the side surface of the upper liner 6U towards the inside of the upper liner 6U, for example. The plurality of holes 6b are holes for placement of heaters 21 in the upper liner 6U to heat the upper die 8U. In the example shown in FIG. 2, the plurality of holes 6b extend in the right-left direction and are arranged at intervals in the depth direction in the figure.
As described above, the heater 21 is disposed in each of the plurality of holes 6b.
In the die apparatus 1 according to an embodiment, the gap between the groove 6a or the hole 6b in the upper liner 6U and the heater 21 may be filled with a filler 31 such as putty with good thermal conductivity.
In the die apparatus 1 according to an embodiment, the upper liner 6U is detachably held by the upper holder 5U.
As described below, when it is not necessary to heat the upper die 8U by the heater 21, the upper liner 6U is removed from the upper die unit 1U, and an unshown liner without the heater 21 and the groove 6a or hole 6b for placement of the heater 21 is attached to the upper die unit 1U.
The upper die 8U is a die with a plate pattern formed on the lower surface thereof for press forming a thin metal sheet, which is a workpiece 11 to be processed by the die apparatus 1 according to an embodiment, into a desired shape.
In the present embodiment, the workpiece 11 is, for example, a thin metal sheet with a thickness of 1 mm or less.
In the die apparatus 1 according to an embodiment, the upper die 8U is attached to the lower surface of the upper liner 6U. In other words, the upper liner 6U is held above the upper die 8U by the upper holder 5U.

(Lower die unit 1L)

In the die apparatus 1 according to an embodiment, the lower die unit 1L includes a lower holder 5L, a lower liner 6L, a die liner 7, and a lower die 8L as main components.
The lower holder 5L is a holder for holding the lower die 8L of the pair of upper and lower dies 8, the die liner 7, and the lower liner 6L.
The lower liner 6L is a liner that is disposed between the lower holder 5L and the die liner 7 and is held by the lower holder 5L together with the lower die 8L. The lower liner 6L has a heater 21 attached, as described below, and is a separate member from the pair of upper and lower dies 8.
In the die apparatus 1 according to an embodiment, the lower liner 6L is attached to the upper surface of the lower holder 5L.
In the die apparatus 1 according to an embodiment, the upper surface of the lower liner 6L has a plurality of grooves 6a. The plurality of grooves 6a are grooves for placement of heaters 21 in the lower liner 6L to heat the lower die 8L. In the example shown in FIG. 2, the plurality of grooves 6a extend in the depth direction and are arranged at intervals in the right-left direction in the figure.
As described above, the heater 21 is disposed in each of the plurality of grooves 6a.
In the die apparatus 1 according to an embodiment, a plurality of holes (not shown) may be formed from the side surface of the lower liner 6L towards the inside of the lower liner 6L, for example. The plurality of holes may extend in the right-left direction and may be arranged at intervals in the depth direction in the figure, as with the above-described plurality of holes 6b in the upper liner 6U. The plurality of holes may be provided with heaters 21 to heat the lower die 8L, as with the above-described plurality of holes 6b in the upper liner 6U.
In the die apparatus 1 according to an embodiment, the gap between the groove 6a or the hole (not shown) in the lower liner 6L and the heater 21 may be filled with a filler 31 such as putty with good thermal conductivity.
In the die apparatus 1 according to an embodiment, the lower liner 6L is detachably held by the lower holder 5L.
As described below, when it is not necessary to heat the lower die 8L by the heater 21, the lower liner 6L is removed from the lower die unit 1L, and an unshown liner without the heater 21 and the groove 6a or the like for placement of the heater 21 is attached to the lower die unit 1L.
The die liner 7 is a liner that is disposed between the lower liner 6L and the lower die 8L.
In the die apparatus 1 according to an embodiment, the die liner 7 is attached to the upper surface of the lower liner 6L. The die liner 7, for example, serves as a height adjusting member to place the lower die 8L at a desired height position.
The lower die 8L is a die with a plate pattern formed on the upper surface thereof for press forming the workpiece 11 into a desired shape.
In the die apparatus 1 according to an embodiment, the lower die 8L is attached to the upper surface of the die liner 7. In other words, the lower liner 6L is held below the lower die 8L by the lower holder 5L.

(Advantages of die apparatus 1 according to one embodiment)

The die apparatus 1 according to an embodiment can form irregularities on the workpiece 11. Here, if relatively high forming accuracy is required for the workpiece 11 after forming, the effect of variations in the tensile strength of the workpiece 11 may not be ignored.
The tensile strength of the workpiece 11 depends on the temperature of the workpiece 11 as well as the variation allowed by the material specifications of the workpiece 11. Therefore, for example, when the tensile strength of the workpiece 11 is near the upper limit of the range allowed by the material specifications of the workpiece 11, the tensile strength of the workpiece 11 may further increase in environments with low ambient temperature, such as in winter, and there is a risk that a specified pressing pressure may be insufficient to achieve the required forming accuracy of the workpiece 11 after forming.
In such cases, it is conceivable to take measures such as extending the holding time during which the workpiece 11 is held under pressure or increasing the pressing pressure, for example. However, extended holding time leads to a decrease in productivity due to the longer time required for the pressing process. Alternatively, increasing the pressing pressure is a measure, provided that the increased pressing pressure remains within the pressure capacity of the forming press machine 3.
However, if there is little margin in the pressure capacity of the forming press machine 3, it may be difficult to address the issue by increasing the pressing pressure.
Therefore, in the die apparatus 1 according to an embodiment, for example, when the need to increase the pressing pressure of the forming press machine 3 arises as described above but there is little margin in the pressure capacity of the forming press machine 3, the tensile strength of the workpiece 11 is suppressed by raising the temperature of the workpiece 11.
In the die apparatus 1 according to an embodiment, for example, the temperature of press surfaces 8a of the upper die 8U and the lower die 8L can be maintained at 80°C or lower in a winter temperature environment by controlling the output of the heater 21 using the heater control device 9. In the die apparatus 1 according to an embodiment, for example, the temperature of the press surface 8a is set to 60°C.
As a result of the inventors' intensive study, it was found that, for example, when a stainless steel sheet with a thickness of 0.8 mm as the workpiece 11 is formed using the die apparatus 1 according to an embodiment with the press surface 8a maintained at 60°C in a winter temperature environment, the temperature of the press-formed workpiece 11 becomes approximately 40°C after applying the forming pressure to the workpiece 11 for a holding time of 5 seconds.
In other words, by press forming the workpiece 11 while raising the temperature of the workpiece 11 by the die apparatus 1 according to an embodiment, the workpiece 11 can be press formed while the tensile strength of the workpiece 11 is suppressed by raising the temperature of the workpiece 11, and the same forming accuracy can be obtained as in the case of press forming in a relatively warm environment other than winter.
As described above, the die apparatus 1 according to an embodiment includes the pair of upper and lower dies 8, and the heater 21 for heating the dies 8.
With the die apparatus 1 according to an embodiment, when press forming the workpiece 11 with the dies 8 heated by the heater 21, heat is transferred from the dies 8 to the workpiece 11, so that the temperature of the workpiece 11 rises. This temperature rise suppresses the tensile strength of the workpiece 11. As a result, it is possible to stabilize the forming accuracy of the workpiece 11 press formed by the forming press machine 3, without extending the holding time during which the workpiece 11 is held under pressure or increasing the pressing pressure.
The die apparatus 1 according to an embodiment includes the upper liner 6U and the lower liner 6L, to which the heater 21 is attached and which are separate members from the pair of upper and lower dies 8. This eliminates the need to machine the dies 8 to install the heater 21, thereby ensuring the strength of the dies 8.
In the die apparatus 1 according to an embodiment, the heater 21 is attached to each of the upper liner 6U and the lower liner 6L.
As a result, the temperature of the upper die 8U can be raised by the upper liner 6U with the heater 21, and the temperature of the lower die 8L can be raised by the lower liner 6L with the heater 21. Therefore, the temperature of the workpiece 11 can be raised stably during press forming, and the forming accuracy of the press-formed workpiece 11 can be stabilized.
In the die apparatus 1 according to an embodiment, the upper liner 6U is held above the upper die 8U by the upper holder 5U, and the lower liner 6L is held below the lower die 8L by the lower holder 5L.
As a result, the upper liner 6U and the lower liner 6L with the heater 21 can be efficiently arranged in the die apparatus 1. Additionally, with the die apparatus 1 according to an embodiment, compared to the case where the dies 8 are heated from the side, when the area of the upper and lower surfaces of the dies 8 is larger than the area of side surfaces as in the dies 8 according to an embodiment, heat is transferred from the upper and lower surfaces of the dies 8 as in the die apparatus 1 according to an embodiment, so that the dies 8 can be heated efficiently.
In the die apparatus 1 according to an embodiment, since the upper liner 6U is detachably held by the upper holder 5U, and the lower liner 6L is detachably held by the lower holder 5L, the upper liner 6U and the lower liner 6L can be removed from the die apparatus 1 when there is no need to heat the dies 8 by the heater 21, for example, as the temperature environment around the forming press machine 3 is relatively warm.
This reduces the load on the upper liner 6U and the lower liner 6L and extends their lifespan.
In the die apparatus 1 according to an embodiment, the upper liner 6U and the lower liner 6L may have at least one of grooves 6a or holes 6b for placement of the heater 21.
As a result, the heater 21 can be easily installed in the upper liner 6U and the lower liner 6L.
In the die apparatus 1 according to an embodiment, the surface temperature of the press surface 8a of the pair of upper and lower dies 8 heated by the heater 21 is 80°C or lower.
With the die apparatus 1 according to an embodiment, the tensile strength can be suppressed without, for example, conventional thermal refining for a metallic workpiece 11.
In the die apparatus 1 according to an embodiment, the workpiece 11 is a thin metal sheet with a thickness of 1 mm or less.
With the die apparatus 1 according to an embodiment, the forming accuracy of the thin metal sheet can be stabilized.

(Press-forming method)

A press-forming method using the die apparatus 1 according to an embodiment will now be described.
FIG. 3 is a flowchart showing the processing procedure in the press-forming method using the die apparatus 1 according to an embodiment. The press-forming method according to the present embodiment is carried out, for example, by the forming press machine 3 shown in FIG. 1.
In the press-forming method according to the present embodiment, prior to press forming of the workpiece 11, the heating of the dies 8 by the heater 21 is started (step S1).
In step S1, the heater control device 9 starts energizing each heater 21 and controls the power supply to each heater 21 to maintain a predetermined set temperature.
For example, in step S1, the set temperature of the heater 21 is a temperature that takes into account the deviation from the temperature of the press surface 8a. If the temperature of the press surface 8a becomes, for example, 20°C lower than the set temperature of the heater 21, the set temperature of the heater 21 is set to a temperature 20°C higher than the target temperature of the press surface 8a.
The heater control device 9 may be configured to independently control the temperature of each heater 21 installed in the upper liner 6U and each heater 21 installed in the lower liner 6L. This allows appropriate temperature control, i.e., temperature control such that the difference between the temperature of the press surface 8a of the upper die 8U and the temperature of the press surface 8a of the lower die 8L is reduced even when the thermal capacities of the upper die unit 1U and the lower die unit 1L are different.
After the heater 21 starts to heat the dies 8, it waits until a specified time has elapsed (step S3).
The specified time is the time it takes from the start of heating the dies 8 by the heater 21 until the press surface 8a reaches a specified temperature (e.g., 60°C).
Instead of waiting for the specified time to elapse, the temperature of the press surface 8a may be measured as appropriate, and it may be waited until the press surface 8a reaches the specified temperature.
After waiting, the workpiece 11 is placed on the press surface 8a of the lower die 8L (step S7), and the press forming is performed by the forming press machine 3 (step S7).
The press-formed workpiece 11 is then removed from the die apparatus 1 (step S9).
After that, if the forming operation is to be finished (positive in step S11), the press forming process ends, and if the forming operation is to be continued (negative in step S11), the process returns to step S5.
As described above, in the press-forming method according to the present embodiment, the die apparatus 1 according to an embodiment is used to press form the workpiece 11 by the forming press machine 3.
As a result, it is possible to stabilize the forming accuracy of the workpiece 11 press formed by the forming press machine 3, without extending the holding time during which the workpiece 11 is held under pressure or increasing the pressing pressure.
The present disclosure is not limited to the embodiments described above, but includes modifications to the embodiments described above, and embodiments composed of combinations of those embodiments.
For example, the above-described workpiece 11 is a thin stainless steel sheet with a thickness of 0.8 mm, for example, but the thickness and material of the workpiece 11 need not be the above-described thickness and material.
In the die apparatus 1 according to an embodiment, the thickness of the workpiece 11 may be, for example, 1.0 mm or less. Further, in the die apparatus 1 according to an embodiment, the material of the workpiece 11 is not limited to stainless steel, but may be titanium, aluminum, phosphor bronze, or various other metallic materials.
The die apparatus 1 according to an embodiment does not have to be operated in an environment where the ambient temperature is low, such as in winter as described above. For example, the die apparatus 1 according to an embodiment may be used in a relatively warm temperature environment, for example, when there is a need to press form the workpiece 11 with controlled tensile strength.
The contents described in the above embodiments would be understood as follows, for instance.

(1) A forming press die apparatus 1 according to at least one embodiment of the present disclosure is a forming press die apparatus 1 used in a forming press machine 3, including: a pair of upper and lower dies 8; and a heater 21 for heating the dies 8.
With the above configuration (1), when press forming the workpiece 11 with the dies 8 heated by the heater 21, heat is transferred from the dies 8 to the workpiece 11, so that the temperature of the workpiece 11 rises. This temperature rise suppresses the tensile strength of the workpiece 11. As a result, it is possible to stabilize the forming accuracy of the workpiece 11 press formed by the forming press machine 3, without extending the holding time during which the workpiece 11 is held under pressure or increasing the pressing pressure.
(2) In some embodiments, in the above configuration (1), the die apparatus may include a liner (upper line 6U, lower liner 6L) to which the heater 21 is attached and which is a separate member from the pair of upper and lower dies 8.
With the above configuration (2), there is no need to machine the dies 8 to install the heater 21, so that the strength of the dies 8 can be ensured.
(3) In some embodiments, in the above configuration (2), the pair of upper and lower dies 8 includes an upper die 8U and a lower die 8L. In some embodiments, in the above configuration (2), the die apparatus includes: an upper holder 5U for holding the upper die 8U of the pair of upper and lower dies 8; and a lower holder 5L for holding the lower die 8L of the pair of upper and lower dies 8. The liner (upper liner 6U, lower liner 6L) may include: an upper liner 6U held by the upper holder 5U together with the upper die 8U; and a lower liner 6L held by the lower holder 5L together with the lower die 8L. The heater 21 may be attached to each of the upper liner 6U and the lower liner 6L.
With the above configuration (3), the temperature of the upper die 8U can be raised by the upper liner 6U with the heater 21, and the temperature of the lower die 8L can be raised by the lower liner 6L with the heater 21. Therefore, the temperature of the workpiece 11 can be raised stably during press forming, and the forming accuracy of the press-formed workpiece 11 can be stabilized.
(4) In some embodiments, in the above configuration (3), the upper liner 6U is held above the upper die 8U by the upper holder 5U, and the lower liner 6L is held below the lower die 8L by the lower holder 5L.
With the above configuration (4), the upper liner 6U and the lower liner 6L with the heater 21 can be efficiently arranged in the forming press die apparatus 1.
(5) In some embodiments, in the above configuration (3) or (4), the upper liner 6U is held detachably by the upper holder 5U, and the lower liner 6L is held detachably by the lower holder 5L.

With the above configuration (5), the upper liner 6U and the lower liner 6L can be removed from the forming press die apparatus 1 when there is no need to heat the dies 8 by the heater 21, for example, as the temperature environment around the forming press machine 3 is relatively warm.
This reduces the load on the upper liner 6U and the lower liner 6L and extends their lifespan.
(6) In some embodiments, in any of the above configurations (3) to (5), the upper liner 6U and the lower liner 6L may have grooves 6a or holes 6b for placement of the heater 21.
With the above configuration (6), the heater 21 can be easily installed in the upper liner 6U and the lower liner 6L.
(7) In some embodiments, in any of the above configurations (1) to (6), a surface temperature of a press surface 8a of the pair of upper and lower dies 8 heated by the heater 21 may be 80°C or lower.
With the above configuration (7), the tensile strength can be suppressed without, for example, conventional thermal refining for a metallic workpiece 11.
(8) In some embodiments, in any one of the above configurations (1) to (7), a workpiece 11 to be processed by the pair of upper and lower dies 8 may be a thin metal sheet with a thickness of 1 mm or less.
With the above configuration (8), the forming accuracy of the thin metal sheet can be stabilized.
(9) A press-forming method according to at least one embodiment of the present disclosure is to press form a workpiece 11 by a forming press machine 3 using the forming press die apparatus 1 described in any one of the above configurations (1) to (8).
With the above method (9), it is possible to stabilize the forming accuracy of the workpiece 11 press formed by the forming press machine 3, without extending the holding time during which the workpiece 11 is held under pressure or increasing the pressing pressure.

Reference Signs List

1: Forming press die apparatus (Die apparatus)
1U: Upper die unit
1L: Lower die unit
3: Forming press machine
5U: Upper holder
5L: Lower holder
6U: Upper liner
6L: Lower liner
6a: Groove
6b: Hole
7: Die liner
8: Die
8U: Upper die
8L: Lower die
8a: Press surface
9: Heater control device
11: Workpiece
21: Heater

Claims

A forming press die apparatus used in a forming press machine, comprising:
a pair of upper and lower dies; and

a heater for heating the dies.
The forming press die apparatus according to claim 1, comprising a liner to which the heater is attached and which is a separate member from the pair of upper and lower dies.
The forming press die apparatus according to claim 2,
wherein the pair of upper and lower dies includes an upper die and a lower die,

wherein the die apparatus comprises:
an upper holder for holding the upper die of the pair of upper and lower dies; and

a lower holder for holding the lower die of the pair of upper and lower dies,

wherein the liner includes:
an upper liner held by the upper holder together with the upper die; and

a lower liner held by the lower holder together with the lower die, and

wherein the heater is attached to each of the upper liner and the lower liner.
The forming press die apparatus according to claim 3,
wherein the upper liner is held above the upper die by the upper holder, and

wherein the lower liner is held below the lower die by the lower holder.
The forming press die apparatus according to claim 3 or 4,
wherein the upper liner is held detachably by the upper holder, and

wherein the lower liner is held detachably by the lower holder.
The forming press die apparatus according to claim 3 or 4,
wherein the upper liner and the lower liner have grooves or holes for placement of the heater.
The forming press die apparatus according to claim 1 or 2,
wherein a surface temperature of a press surface of the pair of upper and lower dies heated by the heater is 80°C or lower.
The forming press die apparatus according to claim 1 or 2,
wherein a workpiece to be processed by the pair of upper and lower dies is a thin metal sheet with a thickness of 1 mm or less.
A press-forming method of press forming a workpiece by a forming press machine using the forming press die apparatus according to claim 1 or 2.